use of fan during sleep and the risk of sudden infant death syndrome
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Use of Fan During Sleep and the Risk of Sudden Infant Death
Syndrome
De-Kun Li, MD, PhD
Division of Research
Kaiser Permanente
Oakland, California
March 24, 2009
Background
What do we know about SIDS etiology?
Heterogeneity in etiology – diagnosis by exclusion
Underlying Biological
Susceptibility
Underlying Biological
Susceptibility
Brain Stem
Heart Problem
EnvironmentalTriggers
EnvironmentalTriggers
Sleep Environment
AirPollution
SIDS RISK
First 9 months
SIDS RISK WITH AGE
Infections
Brain Stem
Deficiency
Brain Stem
Deficiency
Resuscitation CapabilityResuscitation Capability
ThermoregulationThermoregulation
Prenatal ExposurePrenatal Exposure
GeneticFactors?GeneticFactors?
GestationalDiabetes
GestationalDiabetes
PreeclampsiaPreeclampsia
InfectionInfection
Maternal smokingMaternal smoking
SleepEnvironment
SleepEnvironment
Sleep PositionSleep Position
Pacifier UsePacifier Use
Soft BeddingSoft Bedding
Fan UseFan Use
Bed SharingBed Sharing
Background
Sleep environment matters
Oxygen deprivation
CO2 re-breathing?
Thermal factor?
Other factors?
Objectives
To examine whether use of a fan in the room impacts the risk of SIDS
To examine whether any other factors influence the relationship between use of a fan and the risk of SIDS
To examine whether opening of a window also has a similar effect on the risk of SIDS as use of a fan
Study Design
Population-based case-control study
Study population
All confirmed SIDS cases in 11 counties in California
Infant age-, ethnicity-matched controls in the same county
English or Spanish speaking
Participation rate: 50% in cases and 41% in controls
Study Design
In-person interview
Use of a fan during the last sleep
Sleep positions
Sleep environment (co-sleep, pacifier, etc)
Other risk factors for SIDS
Statistical analysis
Logistic regression to adjust for confounders
Stratification for evaluating interaction
Comparison with birth certificate data to assess participation bias
Table 1. Characteristics of the Study Population
Characteristic
Cases Controls
(n = 185) (n = 312) aOR (95% CI)*
N (%) N (%)
Maternal Characteristics
Race/ Ethnicity
White 59 (31.9) 119 (38.1) 1.00†
Black 34 (18.4) 59 (18.9) 0.96 (0.52, 1.76)
Latino 61 (33.0) 98 (31.4) 1.22 (0.67, 2.19)
Other 31 (16.8) 36 (11.5) 2.23 (1.13, 4.39)
Age (years)
< 20 25 (13.5) 27 (8.7) 1.80 (0.88, 3.70)
20 - 24 55 (29.7) 54 (17.3) 1.86 (1.12, 3.09)
≥ 25 105 (56.8) 231 (74.0) 1.00†
Table 1. Characteristics of the Study Population (Cont.)
Characteristic
Cases Controls
(n = 185) (n = 312) aOR (95% CI)*
N (%) N (%)
Maternal Characteristics (cont.)
Education
≤ 12 113 (61.1) 141 (45.2) 1.31 (0.81, 2.13)
> 12 72 (38.9) 171 (54.8) 1.00†
Marital Status
Married 93 (50.3) 206 (66.0) 1.00†
Cohabiting 61 (33.0) 72 (23.1) 1.49 (0.87, 2.52)
Single 31 (16.8) 34 (10.9) 1.79 (0.93, 3.47)
Region
Northern CA 115 (35.3) 211 (64.7) 1.00†
Southern CA 70 (40.9) 101 (59.1) 1.07 (0.68, 1.68)
Table 1. Characteristics of the Study Population (Cont.)
Characteristic
Cases Controls
(n = 185) (n = 312) aOR (95% CI)*
N (%) N (%)
Maternal Characteristics (cont.)
Parity (Prior To Index Birth)
0 57 (30.81) 132 (42.3) 1.00†
1 69 (37.3) 96 (30.8) 1.51 (0.91, 2.51)
2 32 (17.3) 52 (16.7) 1.46 (0.77,2.80)
≥ 3 27 (14.6) 32 (10.3) 2.16 (1.02, 4.59)
Smoked During Pregnancy
No 137 (74.5) 265 (85.2) 1.00†
Yes 47 (25.4) 46 (14.8) 1.91 (1.14, 3.28)
Wks Gestation at First Prenatal Visit
< 12 120 (65.6) 238 (77.8) 1.00†
≥ 12 63 (34.4) 68 (22.2) 1.59 (1.00, 2.53)
Table 1. Characteristics of the Study Population (Cont.)
Characteristic
Cases Controls
( n = 185) (n = 312) aOR (95% CI)*
N (%) N (%)
Infant Characteristics
Age (Months)
< 2 45 (24.3) 62 (19.9) 1.57 (0.87, 2.81)
2 - 3 90 (48.7) 155 (49.7) 1.08 (0.66, 1.76)
≥ 4 Months 50 (27.0) 95 (30.5) 1.00†
Birth Weight (Grams)
≥ 2500 148 (81.8) 297 (95.5) 1.00†
< 2500 33 (18.2) 14 (4.5) 4.90 (2.34, 10.26)
Infant Health During Previous 48 Hours
No Illness 107 (58.5) 196 (62.8) 1.00†
Sick, No Fever 67 (36.6) 109 (34.9) 1.20 (0.78, 1.85)
Sick with Fever 9 (4.9) 7 (2.2) 2.6 (0.84, 8.03)
Table 1. Characteristics of the Study Population (Cont.)
Characteristic
Cases Controls
(n = 185) (n = 312) aOR (95% CI)*
N (%) N (%)
Infant Characteristics (cont.)
Premature (< 37 Wks Gestation)
No 150 (81.2) 287 (92.0) 1.00†
Yes 35 (18.9) 25 (8.0) 2.96 (1.58, 5.54)
Sleep Environment
Last Sleep Position
On Back 52 (31.1) 175 (56.1) 1.00†
On Stomach or Side 115 (68.9) 137 (43.9) 2.74 (1.79, 4.21)
Used a Pacifier
No 162 (95.9) 236 (76.4) 1.00†
Yes 7 (4.1) 73 (23.6) 0.10 (0.04, 0.23)
Table 1. Characteristics of the Study Population (Cont.)
Characteristic
Cases Controls
(n = 185) (n = 312) aOR (95% CI)*
N (%) N (%)
Sleep Environment (cont.)
Room Temp (°F)
≤ 70 96 (69.1) 176 (61.5) 1.00†
> 70 43 (30.9) 110 (38.5) 0.65 (0.40, 1.06)
Soft Bedding Under Infant
No 125 (76.2) 250 (80.4) 1.00†
Yes 39 (23.8) 61 (19.6) 0.95 (0.57, 1.59)
Soft Sleep Surface
No 153 (87.9) 289 (93.2) 1.00†
Yes 21 (12.1) 21 (6.8) 1.36 (0.68, 2.71)
Covers Over Head
No 147 (88.6) 297 (95.5) 1.00†
Yes 19 (11.5) 14 (4.5) 3.13 (1.40, 7.02)
Table 1. Characteristics of the Study Population (Cont.)
Characteristic
Cases Controls
(n = 185) (n = 312) aOR (95% CI)*
N (%) N (%)
Sleep Environment (cont.)
Bed Sharing Status
Slept Alone 103 (59.9) 195 (67.2) 1.00†
Slept with Parent(s) Only 45 (26.2) 79 (27.2) 1.01 (0.61, 1.68)
Slept with Non-Parent(s)# 24 (14.0) 16 (5.5) 2.86 (1.35, 6.07)
Regular Smoking in Home Postpartum
No 164 (89.1) 291 (94.2) 1.00†
Yes 20 (10.9) 18 (5.8) 1.50 (0.68, 3.31)
*Odds ratio and 95% confidence interval adjusted for race/ethnicity, maternal age, education, region, smoking during pregnancy, infant age, birth year and last sleep position unless the variable itself was the exposure of interest. Maternal race/ethnicity, infant age at last sleep, and region are matching variables.†Reference group#Presence of other individuals (with or without parents)
Table 2. Use of a Fan or having an open window in
Relations to SIDS Risk*
Characteristic
Cases Controls
(n = 185) (n = 312) aOR (95% CI)†
N (%) N (%)
Fan on in Room at Last Sleep
No 161 (96.4) 273 (88.4) 1.00‡
Yes 6 (3.6) 36 (11.7) 0.28 (0.10, 0.77)
Window Open in Room at Last Sleep
No 136 (84.0) 232 (75.1) 1.00‡
Yes 26 (16.1) 77 (24.9) 0.64 (0.33, 1.21)
Table 3. The Effect of Fan Use on SIDS Risk by Sleep
Environment
Characteristic
Cases Controls
(n = 185) (n = 312) aOR (95% CI)†
N (%) N (%)
Room Temperature
Room Temperature ≤ 70° F at Last Sleep
No Fan 91 (94.8) 163 (93.1) 1.00‡
Fan On 5 (5.2) 12 (6.9) 0.77 (0.22, 2.73)
Room Temperature > 70° F at Last Sleep
No Fan 41 (97.6) 88 (80.0) 1.00‡
Fan On 1 (2.4) 22 (20.0) 0.06 (0.01, 0.52)
Table 3. The Effect of Fan Use on SIDS Risk by Sleep
Environment (Cont.)
CharacteristicCases Controls
(n = 185) (n = 312) aOR (95% CI)†
N (%) N (%)
Window Closure
Room with Window Closed at Last Sleep
No Fan 132 (98.5) 211 (91.0) 1.00‡
Fan On 2 (1.5) 21 (9.1) 0.15 (0.03, 0.71)
Room with Window Open at Last Sleep
No Fan 22 (84.6) 62 (80.5) 1.00‡
Fan on 4 (15.4) 15 (19.5) 0.73 (0.17, 3.08)
Placed on Back at Last Sleep
No Fan 48 (94.1) 156 (90.2) 1.00‡
Fan On 3 (5.9) 17 (9.8) 0.84 (0.21, 3.39)
Placed Prone or on Side at Last Sleep
No Fan 108 (97.3) 117 (86.0) 1.00‡
Fan on 3 (2.7) 19 (14.0) 0.14 (0.03, 0.55)
Table 3. The Effect of Fan Use on SIDS Risk by Sleep
Environment (Cont.)
Characteristic
Cases Controls
(n = 185) (n = 312) aOR (95% CI)†
N (%) N (%)
Bed Sharing
Slept Alone at Last Sleep
No Fan 93 (96.9) 169 (86.7) 1.00‡
Fan On 3 (3.1) 26 (13.3) 0.23 (0.06, 0.90)
Slept with Parents only at Last Sleep
No Fan 44 (47.8) 75 (94.9) 1.00‡
Fan On 1 (2.2) 4 (5.1) 0.40 (0.03, 4.68)
Slept with Non-Parents at Last Sleep§
No Fan 22 (95.6) 11 (68.8) 1.00‡
Fan on 1 (4.3) 5 (31.3) 0.15 (0.01, 1.85)
Table 3. The Effect of Fan Use on SIDS Risk by Sleep
Environment (Cont.)
Characteristic
Cases Controls
(n = 185) (n = 312) aOR (95% CI)†
N (%) N (%)
Pacifier Use
Used Pacifier at Last Sleep
No Fan 6 (85.7) 65 (89.0) 1.00‡
Fan On 1 (14.3) 8 (11.0) 1.99 (0.16, 24.4)
No Pacifier Used at Last Sleep
No Fan 153 (96.8) 206 (88.0) 1.00‡
Fan On 5 (3.2) 28 (12.0) 0.22 (0.07, 0.69)
Limitations
Low participation rate
Adjustment for socio-demographic factors
Strong protective effect ---- strong participation bias
Compare to birth certificate data
Recall bias? Adjusting for recall interval
Comparison between Participants and Source Population
Risk Factor
Participants
Cases (n= 179) / Controls (n= 304)
Source Population
All cases (n= 348)/ ethnically matched controls (n = 10010)
OR 95% C.I. OR 95% C.I. Maternal age < 20 years 2.1 1.2-3.6 1.5 1.1-2.0 Mother’s education < 12th grade
1.9
1.3-2.8
1.7
1.4-2.2
Parity > 3 2.6 1.6-4.4 1.8 1.4-2.3 Birth weight < 2500 gms 4.8 2.6-9.1 3.2 2.4-4.2
Male Infant 1.0 0.7-1.4 1.5 1.2-1.8 Gestational age at initial prenatal visit > 5 months
1.5
0.8-2.5
1.6
1.1-2.0
Limitations
Limited information related to fan use• Duration• Location• Type of fan used (ceiling, floor, etc)• Orientation of the fan (facing or away)
Conclusions
Use of fan in the sleeping room may reduce the risk of SIDS
The finding is consistent with other known factors in the sleep environment that influence the SIDS risk
Use of a fan could be another simple and effective way to further reduce SIDS
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